Principal stress angle

[[Ed...]]

Hi, I'm wondering if there's any way I can get the principal stress angle? I do have the vector field of the principal stress direction, but I actually needed to know the vector's angle... I've spent hours on this but haven't been able to find a solution yet. Every help is much appreciated. Thanks in advance!

Edited June 29, 2021

[[St...]]

Hi Eduarda,

the software can't do this out of the box. Its also a question of definition of the angle. Angle between vector and ?? ?

Please find two scripts attached. Theses scripts does not calculate angles, but exporting this vectors for each facet in a csv file. So you can calculate the angles by yourself in your own definition.

Hope that helps!

 

Best regards

Steffen

 

export_major_strain_directions.py export_minor_strain_directions.py

[[Th...]]

Hi Eduarda,

just a short query: What do you mean with "principle stress angle"? Do you have a definition or a sketch? Do you really mean stress or maybe strain?

Just a suggestion: Are you looking for the angle between the 1st principal stress/strain direction and the element's/local x-axis, which you usually can read easily from Mohr's circle?

(source https://en.wikipedia.org/wiki/Mohr's_circle#/media/File:Mohr_Circle_plane_stress_(angle).svg)

In case of strain this is the value you usually will get from strain gauge rosettes and can be computed from the strain tensor provided by GOM Software by (orthogonal):
 (see last formula on sketch from Wikipedia above)

You can create such a value for Surface Components in GOM Software by an User-defined Check.

(You can download/install this definition from the attached *.xml-file.)

If you are really talking about stress, it is more complicated: GOM systems only measure outer surface tangential strains and not stresses, as we have no idea how the force distributes inside the material. Under special circumstances (elastic linear material behavior, only surface tangential shear, ...) you can transform surface tangential strain tensors into stress tensors by using plane-stress- (https://en.wikipedia.org/wiki/Plane_stress) or plane-strain-model (https://en.wikipedia.org/wiki/Infinitesimal_strain_theory#Plane_strain). This can also be done in GOM Software by User-defined Checks, but needs more effort. Maybe we can discuss it in more detail, if it is really what you need.

major_angle.xml

Edited August 9, 2021